Rubber Thickness Measurement


Laser sensors measuring thickness of rubber in calendering operation

Acuity laser sensors are used widely throughout the rubber manufacturing industry. Rubber sheet manufacturers need online sheet thickness measurements for Quality Control and system control feedback loops. Rubber presents several challenges for metrology equipment, including the extremely low surface reflectivity, the dirty measuring environment and the temperature of the material to be measured. Manufacturers demand reliable, non-contact measuring devices to minimize downtime and scrap material production.

A large international rubber conveyor belt manufacturer uses Acuity AR700 laser displacement sensors to measure the thickness of black rubber sheet in a calendering process. After a one-month trial period, the AccuRange 600-4 sensor model (now using AR700-4) was chosen to replace other equipment which failed to meet accuracy requirements. The AR600 sensor is extremely durable and met the environmental requirements for this industrial application.

During calendering and rubber processing, the surface of the rubber sheet is very shiny and very black, creating conditions where little light can be reflected. These are often the most challenging conditions for optical measurement sensor. Acuity installed an upgraded laser diode in the AR600-4, bringing 5 mW of laser power (standard is 1 mW) to get a stronger return signal off the dark surface. The result was excellent sensitivity on the rubber sheet and fast measurement speeds.

This rubber manufacturer monitors the thickness measurements using four sensors positioned at the top, 140 mm (5.5 in.) from the sheet surface. The rubber sheet lays across a roll cylinder. The top of the roller is the reference (zero) surface for thickness measurements. The laser spots aim directly perpendicular to the sheet surface at four different points across the sheet width for this process where the material stretches between two rollers, so that the roller gap can be adjusted accordingly to produce the desired (consistent) sheet thickness.

These same sensors are used by tire manufacturers to measure sheet thickness of sidewall material.

For more information on how Acuity sensors are used to measure rubber sheet thickness, please contact Acuity.

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